Alkylthioethanamine carbamic acid derivatives and their use in biocidal compositions

ABSTRACT

Alkylthioalkylamine carbamic acid derivatives are prepared which correspond to the formula:    &lt;IMAGE&gt;  (I)  wherein R and R1 are both independently alkyl groups containing from 6 to 16 carbon atoms, and m and n are both independently integers of from 2 to 3. Compositions containing these compounds inhibit the growth of organisms such as bacteria, yeast, fungi, mold, algae, mollusks, hydroids, or tunicates on surfaces.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of application Ser. No. 651,892 filed Feb. 7, 1991,now U.S. Pat. No. 5,118,534.

BACKGROUND OF THE INVENTION

This invention relates to a novel compound, and a method of its use forinhibiting the growth of microorganisms and marine organisms onsurfaces.

Problems associated with growth of yeast, mold, fungi, bacteria, andalgae on surfaces like shower stalls include discoloration and possiblyunsanitary surfaces. Current market cleaners which "bleach" outdiscoloration leave little or no residual cleaner to prevent rapidre-growth of organisms.

It would be greatly desirable to have a commercially acceptablecomposition and method of use of the composition to inhibit the growthof such microorganisms and marine organisms by employing an insituproduced or pre-prepared antimicrobial film layer, which remains on thesurface for a considerable length of time.

Alkylthioethylamines and related alkylaminosulfides are known for theirbactericidal activity. Fungi and bacteria have been controlled by use ofalkylthioalkylamines and dithiocarbamates, whereas aquatic weeds havebeen controlled by phenylthioalkylamines.

U.S. Pat. No. 4,816,061 to Walter, Jr., et al., teaches the use ofalkylthioalkylamines for inhibiting microorganisms and/or controllingbiofouling of cooling towers.

Alkali metal carbamates of amines have been used as antioxidants forlubricants, whereas polyamine carbamates have been found useful asvulcanizing agents for fluororubbers.

The desirability of identifying or discovering new antimicrobial agentsis widely recognized for several reasons. These include the developmentof microbe strains resistant to known antimicrobials, the occurrence ofundesirable interactions of certain known antimicrobials with the mediumor product in which the antimicrobial is used, and high toxicity ofcertain known antimicrobials to certain non-target organisms such asmammals.

The present invention solves this problem by disclosing a new compoundwhich may be employed as an antimicrobial for inhibiting the growth ofmicroorganisms or marine organisms on surfaces.

SUMMARY OF THE INVENTION

The present invention is directed to a compound corresponding to theformula: ##STR2## wherein R and R₁ are both independently alkyl groupscontaining from 6 to 16 carbon atoms, and m and n are both independentlyintegers selected from 2 or 3.

The present invention is also directed to a method for inhibiting thegrowth of microorganisms and marine organisms on a surface whichcomprises applying to said surface (i) a first compound corresponding tothe following formula:

    RS(CH.sub.2).sub.m NH.sub.2                                (Formula II)

wherein R is an alkyl group containing from 6 to 16 carbon atoms and mis an integer selected from 2 or 3, and (ii) a second compoundcorresponding to the formula:

    R.sub.1 S(CH.sub.2).sub.n NH.sub.2                         (Formula IIa)

wherein R₁ is an alkyl group containing from 6 to 16 carbon atoms and nis an integer selected from 2 or 3 and wherein the surface is exposed toair during application of the compounds. The first and second compoundsare applied in amounts effective to inhibit the growth of microorganismsand marine organisms on the surface and whereby a film of the compoundof formula: ##STR3## wherein R,R₁, m and n are as defined hereinabove,is formed on the surface.

In another aspect, the present invention relates to the method of use ofthe compound of Formula I for inhibiting growth of microorganisms andmarine organisms on a surface which comprises introducing onto saidsurface a compound corresponding to the formula: ##STR4## wherein R andR₁ are both independently alkyl groups containing from 6 to 16 carbonatoms, and m and n are both independently integers selected from 2 or 3and wherein the compound is introduced in an amount effective to inhibitthe growth of microorganisms and marine organisms on the surface."Introducing onto said surface" is intended to encompass either applyingthe compound directly onto the surface or applying to the surfaceprecursors of the compound which react to form the compound.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to a compound corresponding to the formula:##STR5## wherein R and R₁ are both independently alkyl groups containingfrom 6 to 16 carbon atoms, and m and n are both independently integersof from 2 or 3.

In the compounds of Formula I, it is preferred that m or n is 2. It isalso preferred that R and R₁ are both independently alkyl groupscontaining from 6 to 12 carbon atoms. The most preferred compound isn-decylthioethylaminecarbamic acid derivative, wherein both R and R₁ aredecyl groups and m and n are each the integer 2.

In the present specifications and claims, the term "alkyl" is employedto designate straight and branched chain alkyls. Preferably, the term"alkyl" is employed to designate straight chain alkyls of 6 to 16 carbonatoms and branched chain alkyls of 6 to 16 carbon atoms. Morepreferably, the term "alkyl" is employed to designate straight chainalkyls of 6 to 12 carbon atoms and branched chain alkyls of 6 to 12carbon atoms.

As used herein, the term "film" refers to a covering or a layer of thecompounds of the Formula I or of the Formula II on to a surface exposedto air. Such a film should be at least one molecule thick and may be asthick as 1 millimeter (mm).

As used herein, the term "adventitious carbon dioxide" refers to thatcarbon dioxide which is not inherent or innate to the compound ofFormula II or IIa or a mixture of compounds of Formula II and IIa, butinstead is added from an external source, which in the present inventioncould be the atmospheric carbon dioxide.

As used herein, the term "effective amount" refers to that amount of acompound or a mixture of two or more compounds of this invention, whichis needed to exhibit inhibition or killing of selected organisms.Typically, this amount varies from about 1 part per million (ppm) toabout 100,000 ppm by weight of the formulation. Such amounts varydepending upon the particular compound tested, the targeted organismsand the amount of formulation to be applied to a given area. Also, theexact concentration of the compounds to be added in the treatment ofindustrial and consumer formulations may vary within a product typedepending upon the components of the formulation.

As used herein, the term "inhibit" refers to suppression, control,stasis, killing, retardation or any other interference with the normallife processes of microorganisms such as algae, bacteria, yeast, molds,and marine organisms such as mollusks, hydroids, tunicates, and thelike.

Structural Formula of carbamic acid derivative of alkylthioalkylamine

In the following discussion, R₂ and R₃ simply represent generic alkylgroups.

The chemical structure of the reaction product of aliphatic amine withcarbon dioxide has been reported in U. Mioc and S. Ribnikar (Bull. de laSoc. Chim. Beograd 43 (9), 603-612 (1978), incorporated herein byreference, to be a carbamic acid having the structure as illustrated inthe following equation: ##STR6##

Mioc et. al (Bull. de la Soc. Chim. Beograd, 43 (10), 725-732 (1978))incorporated herein by reference have proposed that the carbamic acid,formed in the reaction of aliphatic amine with carbon dioxide, forms anacid-base pair with the free amine in the reaction mixture asillustrated by the following formula: ##STR7##

By analogy, the initially formed product of the reaction ofalkylthioalkylamine with carbon dioxide in the present invention isenvisaged to be an alkylthioalkylcarbamic acid represented by FormulaIII: ##STR8## The carbamic acid so produced then, presumably, reactsfurther with the free amine to give the carbamic acid derivative similarto the compound of Formula I: ##STR9##

The carboxylation of 2-(octylthio)ethanamine in the present inventionpresumably yields an intermediate carbamic acid of formula: ##STR10##The carbamic acid then reacts with another molecule of2-(octylthio)ethanamine to yield 2-(octylthio)ethanamine carbamic acidderivative of formula: ##STR11##

The structure of the carbamic acid derivative as obtained above has beencharacterized by carbon nuclear magnetic resonance spectroscopy (NMR),infrared spectroscopy (IR), and elemental analysis and is consistentwith the above formula.

PREPARATION

Methods of preparation of the alkylthioalkylamines of Formula II and IIaare known in the art, for example, in U.S. Pat. Nos. 3,291,363 and3,524,719, incorporated herein by reference. They can also be preparedby reacting ethyl oxazoline with a mercaptan i.e., an aliphatic thiol,such as "RSH", with subsequent hydrolysis of the resultant amide toyield the desired amine. Ethyl oxazolines and mercaptans arecommercially available for use as starting materials.

Carboxylation of alkylthioalkylamines of Formula II and IIa to yieldalkylthioalkylcarbamic acid derivatives is achieved by bubbling carbondioxide gas through an acetonitrile solution of alkylthioalkylamine toafford a white precipitate which is recovered by known methods such assuction filtration, centrifugation or similar solid recovery from aheterogeneous mixture.

METHOD OF USE

The method of this invention can be practiced by applying an effectiveamount of a solution, a slurry, a suspension, a paste or a solidcomposition of pre-prepared carbamic acid derivatives of Formula I tosurfaces such as shower stalls, paints, walls, tiles, ships, or pilings,where biocidal activity is desired.

A solution of solid carbamic acid derivatives can be obtained bydissolving the compounds of Formula I into polar aprotic solvents likedimethyformamide.

A solid formulation of carbamic acid derivatives of Formula I can beobtained by mixing the carbamic acid derivative with solid fillers suchas calcium carbonate. A suspension of the carbamic acid derivatives canbe prepared by suspending the carbamic acid derivative in solvents inwhich the carbamic acid derivative is sparingly soluble and suchsuspensions can then be made into pastes or slurries by use ofthickeners such as cellulose ethers.

In another embodiment of this invention, an effective amount of at leastone amine corresponding to each of the Formula II or Formula IIa isapplied in the form of a solution, a slurry, a suspension, a paste, aliquid, or a spray, to a surface of choice exposed to air at the time ofapplication of the amines. The amines of Formula II and Formula IIa canbe the same or different. The solutions of the free amines can be formedby dissolving the free amines of Formula II or IIa into solvents, suchas methylene chloride or acetonitrile. A paste or a slurry of the freeamines may be obtained by mixing liquid alkylthioalkylamines withthickeners such as cellulose ethers. The free amine can also bedispersed in an aerosol material, such as a fluorinated hydrocarbon orother propellant, for use as a spray. In addition to a solvent, diluentor dispersing agent, other adjuvants such as pigments, viscositymodifiers and surface active agents may be present in the formulation.

A preferred application is for the production of biocidal foams sincethe amine can readily be incorporated into a blowing agent such asmethylene chloride along with air.

The free amines on application to a surface will react in-situ withadventitious carbon dioxide present in the atmosphere to produce atleast one carbamic acid derivative which then acts as a biocidal matrix.The carbamic acid derivative typically remains on the surface for atleast five days, depending upon the nature of the surface treated andthe uses made of the surface after the application of a film. Either thecompound corresponding to formula I, a mixture of compounds of formulaII and IIa, or at least one compound corresponding to formula II or IIacan be applied in an amount effective to retard the growth ofmicroorganisms or marine organisms as the situation warrants.

Another application of the present invention is in paint formulations.The amine can react with adventitious carbon dioxide to form anon-leaching film during the process of paint film formation regardlessof paint film formation mechanism.

The following examples are to further illustrate the present inventionbut should not be interpreted as a limitation thereon.

EXAMPLE I Synthesis of 2-(octylthio)ethyl propionamide

1200 g (12.1 moles) of 2-ethyl-2-oxazoline and 1771 g (12.1 moles) of1-octanethiol are mixed in a large beaker and charged into a 5 literround-bottom flask swept with dry nitrogen. 3.944 g (28.9 mmoles) ofpowdered zinc chloride catalyst are added, and the mixture heated at170° C. for about four hours to afford a straw-yellow crude oil whichsolidifies at about 40° C. Fractional distillation gives 2,849 g (yield,96%) of a clear oil, b.p. 166°-179° C. (0.2-0.3 mmHg), which solidifiesupon cooling to a white, waxy, crystalline solid (m.p. 37°-38° C.). Thestructure identity is confirmed by IR, proton NMR, and elementalanalysis.

Hydrolysis of 2-(octylthio)ethyl propionamide to yield2-(octylthio)ethanamine

A liquid (50° C.) melt of n-octylthioethyl propionamide (804.6 g, 3.28moles) is added to 750 ml of concentrated (36.6%) aqueous hydrochloricacid solution in a jacketed 4-liter glass reactor. The stirred mixtureis heated to about 90° C. for about 72 hours. The resulting hot solutionis brought to a pH of about 13 with about 400 ml of 12M aqueouspotassium hydroxide solution, while maintaining the temperature between60°-90° C. After bringing the solution to a pH of 13 and allowing itstand unstirred for about 1/2 hour, a dark brown organic phase cleanlyseparates as the upper phase which is recovered for subsequentdistillation.

Fractional distillation under nitrogen gives 527 g (yield, 71.2%) of aclear oil, b.p. 125°-127° C. (0.3 mmHg), which is identified by IR,proton NMR, and elemental analysis.

Carboxylation of 2-(octylthio)ethanamine to yield a carbamic acidderivative

Carbon dioxide is bubbled through an acetonitrile (60 ml) solution of 10g (52.8 mmoles) of 2-(octylthio)ethylamine to afford a white precipitatewhich is isolated by suction filtration. The product is washed threetimes with 10 ml portions of acetonitrile and is then washed three timeswith 20 mls portions of methyl t-butyl ether. The product is air driedto give 7.77 g of octylthioethylamine carbamic acid derivative as awhite powder (yield, 62.1%). The product is further characterized by IR.proton NMR, and elemental analysis.

EXAMPLE II Synthesis of 2-(decylthio)ethanamine hydrochloride

Approximately 225 pounds of decylmercaptan are loaded into a jacketedreactor equipped with an agitator. 1.25 pounds of zinc chloride catalystare added through the manhole. The system is heated to approximately140° C. and 130 pounds of 2-ethyl-2-oxazoline are added at the rate of 3lbs/min in about 45 minutes. About 30 minutes are allowed for thereaction to be completed, the reactor cooled to approximately 120° C.and 155 pounds of 32 weight percent hydrochloric acid are then added tothe reaction mixture. The reactor is heated to 150°-160° C., at whichtime the vapor pressure of the system is approximately 60 psi. Thetemperature is maintained near 150° C. for 2 hours to complete thehydrolysis.

Synthesis of 2-(decylthio)ethanamine

After the hydrolysis in the above step is complete, the reactor iscooled to about 100° C. and approximately 2.0 equivalents of sodiumhydroxide (217 lbs of 50 weight percent solution), based upon thehydrochloric acid added in the production of 2-(decylthio)ethanaminehydrochloride, are introduced with stirring in approximately 30 minutes.The reaction mixture is allowed to settle until phase separation iscomplete (approximately 30 minutes) and the 2-(decylthio)ethanamine isdecanted off. The 2-(decylthio)ethanamine can be passed over a dryingagent such as sodium sulfate, or may be vacuum stripped to remove anydissolved and/or entrained water.

2-(decylthio)ethanamine can also be recovered from the reaction mixtureby extraction with a water immiscible organic solvent such as toluene ormethylene chloride. The resulting solution can be decanted off from theaqueous phase and dried in the manner described herein above.

Synthesis of the carbamic acid derivative of 2-(decylthio)ethanamine

The carbamic acid salt of 2-(decylthio)-ethanamine can be prepared bybubbling carbon dioxide gas into the organic solution of2-(decylthio)ethanamine obtained as described herein above.

The carbamic acid salt of 2-(decylthio)ethanamine can also be preparedby pouring 2-(decylthio)ethanamine to form a film and exposing the filmto adventitious carbon dioxide or to carbon dioxide from evaporation ofdry ice. The carbon dioxide reacts with the amine to produce carbamicacid derivative of 2-(decylthio)ethanamine.

The carbamic acid derivative can also be prepared by spraying2-(decylthio)ethanamine as a mist into a chamber containing carbondioxide to form the carbamic acid salt of 2-(decylthio)ethanamine.

Biocidal Activity

The compounds of the present invention are useful because of theirbiocidal activity and can be used as antibacterial and/or antifungalagents. Their effectiveness varies with the concentration of thecompound used and the particular organism to be controlled.

The biocidal activity of the compounds of the present invention isdemonstrated by using 2-(decylthio)ethylamine carbamic acid derivative(DTEA carbamic acid derivative) and 2-(octylthio)ethylamine carbamicacid derivative (OTEA carbamic acid derivative) as representativecompounds of the invention.

The minimum inhibitory concentration (MIC) for DTEA and OTEA carbamicacid derivatives is determined for 9 bacteria, using nutrient agar, andfor DTEA carbamic acid derivative for 7 yeast and fungi, using maltyeast agar. A one percent solution of DTEA or OTEA carbamic acidderivative is prepared in a mixture of acetone and water. Nutrient agaris prepared at pH 6.8 representing a neutral medium, and at pH 8.2,representing an alkaline medium. The nutrient agars are prepared byadding 23 g of nutrient agar to one-liter of deionized water. Inaddition, the alkaline medium is prepared by adjusting a 0.04M solutionof N-[tris(hydroxymethyl)methyl]-glycine buffered deionized water withconcentrated sodium hydroxide to a pH of 8.5. Malt yeast agar isprepared by adding 3 g yeast extract and 45 g malt sugar per liter ofdeionized water. The specific agar is dispensed in 30 ml aliquots into25×200 mm test tubes, capped and autoclaved for 15 minutes at 115° C.The test tubes containing the agar are cooled in a water bath until thetemperature of the agar is 48° C. Then, an appropriate amount of the onepercent solution of the test compound is added (except in the controlswhere no compound is added) to the respective test tubes so that thefinal concentrations are 500, 250, 100, 50, 25, 10, 5, 2.5, 1.0 and 0parts per million of the test compound in the agar, thus having a knownconcentration of test compound dispersed therein. Not all compounds weretested at all the concentrations. The contents of the test tubes arethen transferred to respective petri plates. After drying for 24 hours,the petri plates containing nutrient agar are inoculated with bacteriaand those containing malt yeast agar are inoculated with yeast andfungi.

The inoculation with bacteria is accomplished by using the followingprocedure. Twenty-four hour-cultures of each of the bacteria areprepared by incubating the respective bacteria in tubes containingnutrient broth for 24 hours at 30° C. in a shaker. Dilutions of each ofthe 24 hour-cultures are made so that nine separate suspensions (one foreach of the nine test bacteria) are made, each containing 10⁸ colonyforming units (CFU) per ml of suspension of a particular bacteria.Aliquots of 0.3 ml of each of the bacterial suspensions are used to fillthe individual well of Steer's Replicator. For each microbialsuspension, 0.3 ml was used to fill three wells (i.e., three wells of0.3 ml each) so that for the nine different bacteria, 27 wells arefilled. The Steer's Replicator is then used to inoculate both theneutral and alkaline pH nutrient agar petri plates.

The inoculated petri plates are incubated at 30° C. for 48 hours andthen read to determine if the test compound which is incorporated intothe agar prevented growth of the respective bacteria.

The inoculation with the yeast and fungi is accomplished as follows.Cultures of yeast and fungi are incubated for seven days on malt yeastagar at 30° C. These cultures are used to prepare suspensions by thefollowing procedure. A suspension of each organism is prepared by adding10 ml of sterile saline and 10 microliters (μl) of octylphenoxypolyethoxy ethanol (TRITON™ X-100, a trademark of Rohm & Haas Company)to the agar slant of yeast or fungi. The sterile saline/octylphenoxypolyethoxy ethanol solution is then agitated with a sterile swab tosuspend the microorganism grown on the slant. Each resulting suspensionis diluted into sterile saline (1 part suspension: 9 parts sterilesaline). Aliquots of these dilutions are placed in individual wells ofSteer's Replicator and petri plates inoculated as previously described.The petri plates are incubated at 30° C. and read after 48 hours foryeast and 72 hours for fungi.

Table I lists the nine bacteria and seven yeast and fungi used in theMIC test described above along with their respective American TypeCulture Collection (ATCC) identification numbers.

                  TABLE I                                                         ______________________________________                                        Organisms Used In The Minimum                                                 Inhibitory Concentration Test                                                 Organism             ATCC No.                                                 ______________________________________                                        Bacteria                                                                      Bacillus subtilis (Bs)                                                                              8473                                                    Enterobacter aerogenes (Ea)                                                                        13048                                                    Escherichia coli (Ec)                                                                              11229                                                    Klebsiella pneumoniae (Kp)                                                                          8308                                                    Proteus vulgaris (Pv)                                                                               881                                                     Pseudomonas aeruginosa (Pa)                                                                        10145                                                    Pseudomonas aeruginosa (PRD-10)                                                                    15442                                                    Salmonella choleraesuis (Sc)                                                                       10708                                                    Staphylococcus aureus (Sa)                                                                          6538                                                    Yeast/Fungi                                                                   Aspergillus niger (An)                                                                             16404                                                    Candida albicans (Ca)                                                                              10231                                                    Penicillium chrysogenum (Pc)                                                                        9480                                                    Saccharomyces cerevisiae (Sc)                                                                       4105                                                    Trichoderma viride (Tv)                                                                             8678                                                    Aureobasidium pullulan (Ap)                                                                        16622                                                    Fusarium oxysporum (Fo)                                                                            48112                                                    ______________________________________                                    

In Table II and III, the MIC values of DTEA and OTEA carbamic acidderivatives are set forth for the bacteria organisms and yeast/fungiorganisms which are listed in Table I.

                                      TABLE II                                    __________________________________________________________________________    Minimum Inhibitory Concentrations (in ppm) for                                Test Compounds against Bacteria Species                                                ORGANISMS                                                            COMPOUND Bs  Ea Ec  Kp Pv PRD Pa Sc Sa                                        __________________________________________________________________________    DTEA Carbamic                                                                          10  25 10  50 10 50  >50                                                                              10 25                                        acid deriv. pH 6.8                                                            pH 8.2   10  5  5   5  5  >50 >50                                                                              5  2.5                                       OTEA carbamic                                                                          100 1150                                                                             100 100                                                                              50 100 100                                                                              100                                                                              100                                       acid deriv pH 6.8                                                             pH 8.2   25  25 25  25 50 250 37.5                                                                             25 25                                        __________________________________________________________________________

                  TABLE III                                                       ______________________________________                                        Minimum Inhibitory Concentrations (in ppm) for Test                           Compounds against Yeast/Fungi Species at pH 5.5                                       ORGANISMS                                                             COMPOUND  An     Ca      Pc   Sc    Tv  Ap    Fo                              ______________________________________                                        DTEA      250    250     250  250   50  250   250                             Carbamic                                                                      acid                                                                          derivative                                                                    ______________________________________                                    

What is claimed is:
 1. A compound corresponding to the formula:##STR12## wherein R and R₁ are each independently alkyl groupscontaining from 6 to 16 carbon atoms, and m and n are each independentlyintegers selected from 2 or
 3. 2. The compound of claim 1, wherein R andR₁ are each independently alkyl groups containing from 6 to 12 carbonatoms.
 3. The compound of claim 1, wherein R and R₁ are each decylgroups.
 4. The compound of claim 3, wherein m and n are each the integer2.
 5. An antimicrobial composition comprising an inert diluent and anantimicrobially-effective amount of a compound corresponding to theformula ##STR13## wherein R and R₁ are each independently alkyl groupscontaining from 6 to 16 carbon atoms, and m and n are each independentlyintegers selected from 2 or
 3. 6. The antimicrobial composition of claim5 wherein R and R₁ are each independently alkyl groups containing form 6to 12 carbon atoms.
 7. The antimicrobial composition of claim 5 whereinR and R₁ are each decyl groups.
 8. The antimicrobial composition ofclaim 7 wherein m and n are each the integer
 2. 9. The antimicrobialcomposition of claim 5 wherein the compound present in the compositionis in an amount from about 1 part per million to about 100,000 parts permillion by weight of the composition.
 10. The antimicrobial compositionof claim 5 wherein the inert diluent is a polar aprotic solvent.
 11. Theantimicrobial composition of claim 5 wherein the inert diluent iscalcium carbonate.